Stereoselective total synthesis of ieodomycins A and B and revision of the NMR spectroscopic data of ieodomycin B

Article abstract of DOI:10.1021/jo400929m

Stereoselective total synthesis of antimicrobial marine metabolites ieodomycin A and B have been accomplished starting from commercially available 4-pentyn-1-ol featuring strategic application of the Negishi reaction, Kumada coupling, and Crimmins acetate aldol. This revises the proton NMR spectra of ieodomycin B.

Full text of DOI:10.1021/jo400929m

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Stereoselective total synthesis of Ieodomycin A & B and
revision of the NMR spectroscopic data of Ieodomycin B
Sayantan Das, and Rajib Kumar Goswami
J. Org. Chem., Just Accepted Manuscript • DOI: 10.1021/jo400929m • Publication Date (Web): 19 Jun 2013
Downloaded from http://pubs.acs.org on June 25, 2013
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Stereoselective total synthesis of Ieodomycin A & B and revision of the NMR spectroscopic data
of Ieodomycin B
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Sayantan Das and Rajib Kumar Goswami*
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Department of Organic Chemistry,
Indian Association for the Cultivation of Science, Jadavpur,
Kolkata-700032, India.
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Email: ocrkg@iacs.res.in
OH
OH OH
O
OH
OMe
O
O
Ieodomycin B
Ieodomycin A
ABSTRACT:
Stereoselective total synthesis of antimicrobial marine metabolites Ieodomycin A & B have been
accomplished starting from commercially available 4-pentyn-1-ol featuring strategic application of
Negishi reaction, Kumada coupling and Crimmins acetate aldol. This revises the proton NMR spectra
of Ieodomycin B.
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Marine organisms have long been recognized as rich source of useful metabolites with
applications in human benefits. Isolation, identification as well as synthesis of those novel
metabolites and their active analogues are the subjects of great importance1. Marine
antimicrobial agents2 are known to have a major impact to biopharmaceutical industry due to
their broad range of activities against the rapidly growing multidrug resistant bacteria and
pathogens which create several life threatening problems in clinic. Ieodomycins A-D (1-4)
(Figure-1), the antimicrobial secondary metabolites were first discovered by Shin and his
coworkers3 during their bioassay-guided fractionation studies of EtOAc extract of 09ID194
strain, a marine microorganism from Republic of Korea’s southern reef, Ieodo. Ieodomycins A-
D (1-4) inhibit the growth of microbial strains- Bacillus subtilis, Escherichia coli and
Saccharomyces cerevisiae in sub micro molar range. Important bioactivity and interesting
structural features of these molecules have rendered them the attractive targets for synthetic
organic chemists4. As continuation of our5 endeavor to asymmetric synthesis of bioactive natural
product we have embarked on stereoselective total synthesis of Ieodomycins. In this report we
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Figure-1: Structures of Ieodomycins A-D.
OH
OH OH
O
3
11
9
7
1
OMe
5
1
O
O
2
12
OH
O
OH
OH
O
OH
OH
4
3
describe the total synthesis of Ieodomycin A & B which result in the revision of NMR
spectroscopic data of Ieodomycin B. Structurally Ieodomycin B (2) is the δ lactone form of
Ieodomycin A (1) which comprises a trans-1, 3-diol moiety and a long fatty acid side chain
embodied with two conjugated olefins.
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Retrosynthetic analysis of Ieodomycin A & B is depicted in Scheme-1. The key feature in
our synthesis is the application of chiral auxiliary based Crimmins acetate aldol6 to construct the
trans-1, 3-diol moiety. Ieodomycin B (2) could be accomplished from Ieodomycin A (1) by δ-
lactonizaton. Ieodomycin A (1), in turn, could be synthesized from the protected aldehyde 5
which further could be developed from the aldehyde 6 by two consecutive asymmetric acetate
aldol reactions.
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Scheme-1: Retrosynthetic analysis.
OH
OH OH
O
Lactonization
O
OMe
1
O
Crimmins
acetate aldol
2
OTBS
Crimmins
CHO
CHO
6
acetate aldol
5
Our synthetic endeavor began with commercially available 4–pentyn–1–ol (7) which was
subjected to Negishi reaction followed by concomitant quenching with I2 to produce vinyl
iodide7 8 in 89% yield (Scheme-2). Next Kumada coupling7b with vinyl magnesium bromide and
subsequent Swern oxidation8 furnished moderately volatile aldehyde 6 in good yield over two
steps. The aldehyde 6 was then treated with the titanium enolate generated in situ from (R)-
phenyl alanine derived N-acetylthiazolidinethione 99 in presence of TiCl4 and Hunig's base to
provide 10 as major and 11 as minor products (dr.10:11= 4:1) (scheme-2).
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Scheme-2:
5
6
7
a
b
CHO
OH
I
OH
7
8
6
8
9
OH
O
OH
O
S
S
S
c
+
N
N
S
10
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11
Ph
N
Ph
Ph
9
S
S
O
Reagents and conditions: (a) (i) Me3Al, Cp2ZrCl2, DCE, 0ᵒC-rt, 24h then I2, THF, 0ᵒC, 30 min,
89% (b) (i) vinyl magnesium bromide, (Ph3P)4Pd, toluene, 3h, 0ᵒC-rt, 91% (ii) Swern oxidation, -
78ᵒC to 0ᵒC, 2h, 87% (c) 9, TiCl4, DIPEA, CH2Cl2, -40ᵒC to -78ᵒC, 3h, 69%.
The absolute configuration of the originated hydroxyl group was further confirmed by
modified Mosher’s ester method10. Our initial attempts to prepare Mosher’s esters directly from
compounds 10 and 11 following the literature procedure11 furnished an inseparable complex
mixture due to their incomplete derivatization and decomposition. To obtain satisfactory and
reliable results in this direction, we followed Scheme-3. Both the compounds 10 and 11 were
separately converted to corresponding methyl esters12 12 and 14 respectively. Compound 12 was
then treated separately with (S)–(+)– and (R)–(–)-α-methoxy-α-(trifluoromethyl)phenylacetic
acid in presence of 2,4,6-trichlorobenzoyl chloride and Et3N following the reported procedure11
to yield (S)- and (R)-MTPA esters 13 and 13a respectively. Similarly compound 14 was
converted to its corresponding (S)- and (R)-MTPA esters 15 and 15a respectively. All the
1
protons of two pair of Mosher’s esters 13, 13a and 15, 15a were assigned by H NMR. The
negative Δδ values [Δδ = δS - δR] (Scheme-3) obtained for H-2 protons from the set of esters 13
and 13a clearly confirmed the desired (R)-configuration of the originated hydroxyl center. In a
similar way the hydroxyl center of compound 11 was established as expected (S)-configuration
by positive Δδ value acquired for H-2 protons from the esters 15 and 15a.
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Scheme-3:
5
6
7
8
9
10
11
a
a
OH
O
OH
O
10
11
12
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OMe
OMe
14
12
b
b
-0.021
-0.017
OR
-0.004
O
+0.021
+0.019
OR
+0.004
O
-0.070 -0.066
-0.126
-0.022
+0.081 +0.074
+0.020
-0.019
OMe
OMe
+0.049
+0.028
+0.135
+0.060
-0.049
-0.029
+0.023
-0.058
13, R= (S)-MTPA
13a, R= (R)-MTPA
15, R= (S)-MTPA
15a, R= (R)-MTPA
Reagents and conditions: (a) MeOH, imidazole, rt, overnight, (76-78)% (b) S/R –Mosher acid,
2,4,6–trichloridebenzoyl chloride, DMAP, Et3N, toluene, rt, 4h, (75-83)%.
The required amide 10 in our hand was next converted to TBS ether and subsequently
reduced by DIBAL-H to afford the aldehyde 5 with 89% yield over two steps (Scheme-4). The
aldehyde 5 was reacted quickly to (S)–phenylalanine derived N– acetylthiazolidinethione 9 16 to
give 17 as major product and 18 as minor product (dr, 17:18= 5:1). The stereochemistry of 1, 3-
diol moiety of major compound 17 was confirmed further as desired one by C NMR study13
13
from its acetonide 2014 which was prepared in four steps. The required isomer 17 in our hand
was transformed next to methyl ester 19 in presence of MeOH and imidazole12. The prefinal
compound 19 was set to carry out the crucial TBS cleavage to furnish Ieodomycin A (1) and
Ieodomycin B (2) in single step. We have tried a number of reagents (Table-1) with proper
monitoring by thin layer chromatography (TLC) to optimize the formation of compound 1. It
was observed that both AcOH-H2O and CSA worked well to cleave TBS ether to give the
compounds 1 as major and compound 2 as minor products. We preferred CSA in course of our
study due of its short reaction time and easier removal at ambient condition.
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Scheme-4:
5
6
7
OTBS
O
OH
S
OTBS
O
OH
OTBS
CHO
S
a
b
10
+
N
N
S
S
17
5
18
8
9
Ph
Ph
OH
O
10
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12
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Ph
c
OH OH
O
OTBS
O
OH
16
+
d
O
OMe
S
N
OMe
2
1
19
S
O
Reagents and conditions: (a) (i) TBSOTf, 2,6–lutidine, CH2Cl2, 0ᵒC, 15 min. (ii) DIBAL–H, -
78ᵒC, 5 min. 89% over two steps. (b) 16, TiCl4, DIPEA, CH2Cl2, –40ᵒC to –78ᵒC, 3h, 72% with
respect to both compounds 17 & 18. (c) MeOH, imidazole, rt, overnight, 78%. (d) CSA, CH2Cl2:
MeOH (1:1), 0ᵒC, 30 min, 54% with respect to compound 2.
Table-1: Optimization of condition for TBS deprotection by TLC monitoring and observed
qualitative ratio for compound 1 &2.
Entry
Reagent
Solvent
CH2Cl2:MeOH (1:1)
THF
CH2Cl2
-
Temp (ᵒC)
0-rt
0
Time (h)
1
0.5
3
5
Ratio (1:2)
> 9:1
0:1
1:1
> 9:1
1
2
3
4
CSA
TBAF
HF-Pyridine
AcOH-H2O (4:1)
0
0-rt
Our initial attempts to purify both the compounds 1 and 2 by flash chromatography using
silica or silica triturated with Et3N as stationary phase and variety of solvent systems (EtOAc/
hexane, diethyether/hexane, MeOH/CH2Cl2) as mobile phase failed totally to give compound 1
even in moderate yield due to its rapid conversion into more stable δ–lactone 2 within the
column. Finally use of neutral alumina as stationary phase and EtOAc/hexane as mobile phase
served better result in this direction.
During the preparation of this manuscript, a 15 steps synthetic route for Ieodomycins A
& B was published by Koul and his co-workers4b. However there was a mismatch in the
chemical shift of the H-4ax proton of the synthetic compound relative to that reported3 for the
isolated compound.
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The H NMR spectra of our acyclic compound 1 recorded immediately after synthesis
was comparable to the reported data of Ieodomycin A. However, in our hands, unavoidable
counter peaks were generated gradually in the purified acyclic compound due to the spontaneous
formation of the δ-lactone 2. This prevented us to take 13C NMR data of compound 1 due to
requirement of longer time span for its recording. The optical rotation of the pure acyclic
intermediate 1 could not be obtained for the same reason.
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The 13C NMR and optical rotation {reported [α]23 : + 21.0 (c 0.9, CHCl3); observed
D
[α]23 : + 25.8 (c 0.5, CHCl3)} of Ieodomycin B although was in close agreement with our
D
synthetic δ-lactone 2 but a considerable difference was observed in proton NMR spectrum. The
1H NMR spectrum of synthetic δ-lactone 2 exhibited signals for two protons at δ (2.30-2.27)
ppm and one proton at δ 1.52 ppm, where as in the isolation paper3 all those protons appeared at
δ (2.30-2.27) ppm and no proton was reported at δ 1.52 ppm. Eventually COSY, HSQC, HMBC
correlation spectroscopy of our δ-lactone 2 differed from the originals. This observation
prompted us to synthesize all three others possible stereoisomers of Ieodomycin B by analogous
chemistry as adopted for the δ-lactone 2 (Scheme-5).
Scheme-5:
OH
OTBS
O
OH
a
b
18
OMe
O
O
21
2a
OTBS
O
OH
OTBS
O
OH
S
S
S
c
11
+
N
N
S
23
22
a
a
Ph
Ph
OTBS
O
OH
OTBS
O
OH
O
S
OMe
OMe
25
24
N
OH
OH
O
S
16
b
b
Ph
O
O
O
2b
2c
Reagents and conditions: (a) imidazole, MeOH, rt, overnight, (73-77)%. (b) TBAF, THF, 30
min, 0ᵒC, (70-83)%. (c) (i) TBSOTf, 2,6-lutidine, 0ᵒC, 15 min, quantitative; (ii) DIBAL-H,
CH2Cl2, -78ᵒC, 5 min, 88%. (iii) 16, TiCl4, DIPEA, CH2Cl2, -40ᵒC to -78ᵒC, 3h, 68%.
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Compound 18 (Scheme-4) was converted to methyl ester 21 and subsequently TBS ether
was deprotected by TBAF to furnish lactone-2a with 70% yield (Scheme-5). Compound 11 was
subjected next to three steps reaction protocol- protection of alcohol as TBS ether followed by
reduction with DIBAL-H to get an aldehyde which was subjected further to Crimmins acetate
aldol using 16 as an auxiliary to afford expected compound 22 as major and compound 23 as
minor products. Compounds 22 and 23 were next converted separately to methyl ester 24 and 25
by MeOH in presence of imidazole with 76% and 77% yields respectively. Both the esters 24
and 25 were then transformed individually to lactones 2b and 2c in presence of TBAF with 71%
and 83% yields respectively.
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The proton NMR spectra of all stereogenic analogues- 2a, 2b, and 2c made us quite
embraced at the end. Not a single proton NMR spectrum of those isomers matched perfectly with
the reported spectrum. From detailed NMR studies we have seen that the origin of this
discrepancy was mainly attributed by the protons attached with C-4 carbon along with some
ambiguities in coupling constants. Moreover the diastereotopic (H-4)eq and (H-4)ax protons in
that structure3 were shown to resonate in close proximity at δ 2.27 and δ 2.24 ppm respectively
which seemed to be quite contradictory with its architecture15. HSQC correlation spectroscopy of
our δ lactone 2 clearly exibited that one of the C-4 protons would resonate at δ (2.30-2.25) ppm
together with one (H-7)allylic proton where as other would be at δ 1.52 ppm. The large vicinal
coupling (J = 11.5, 8.7 Hz) of H-4 proton resonating at δ1.52ppm with (H-3)ax and (H-5)ax
protons unambiguously support their trans diaxial relationship and hence was assigned as
(H-4)ax. This new assignment was further confirmed by details NOESY as well as by ROESY
correlation spectroscopy which clearly exhibited the anticipated spatial correlations together with
very expected 1, 3-syn di-axial interaction between (H-2)ax and (H-4)ax protons and necessitates
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the revision (see the personal communication16) of the NMR data (Table-2, see supporting
information) of Ieodomycin B.
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In summary, a short, general and very flexible strategy has been developed towards the
synthesis of reported Ieodomycin A and B. This study enabled us to achieve the Ieodomycin B in
9 linear steps with an overall yield of 13%. At the same time an important issue related to the
existence of the acyclic Ieodomycin A in pure form was also discussed. The adopted strategy
paved an easy way for the synthesis of other possible diastereomers of Ieodomycin B and
simultaneously demonstrated the effect of reagents on δ-lactonization of Ieodomycin A to
Ieodomycin B.
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EXPERIMENTAL SECTION:
5
6
(E)-4-Methylhepta-4,6-dienal (6):
7
8
9
To solution of (COCl)2 (1.67 mL, 19.37 mmol) in anhydrous CH2Cl2 (80 mL) at -78ᵒC, DMSO
(2.94 mL, 41.34 mmol) was added in drop wise manner with constant stirring under argon
atmosphere. After 15 min, the (E)-4-methylhepta-4,6-dien-ol7 (1.63 g, 12.92 mmol in 15 mL
anhydrous CH2Cl2) was cannulated to the reaction mixture. After 30 min Et3N (9.01 mL, 64.6
mmol) was added and stirred further 30 min at the same temperature. The reaction was allowed
to warm slowly to 0ᵒC and stirred for 1 h at 0ᵒC. The reaction mixture was quenched with
saturated aqueous NH4Cl (25 mL) and extracted with diethyl ether. The combined organic layers
were washed with saturated NaHCO3, water, brine, dried (Na2SO4) and concentrated in vacuo at
very low temperature. Flash column chromatography (SiO2, 230-400mesh, 3% Et2O in hexane)
gave moderate volatile aldehyde 6 (1.39g, 87%) as colourless oil. Rf = 0.34 (10% Et2O in hexane)
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1
; H NMR (CDCl3, 500MHz): δ9.79(s, 1H), 6.55(dt, J = 17.0, 10.5Hz, 1H), 5.87(d, J = 10.5Hz,
1H), 5.13(d, J= 17.0Hz, 1H), 5.03(d, J= 10.5Hz, 1H), 2.58(t, J=7.5Hz, 1H), 2.40(t, J=7.5Hz,
13
1H), 1.78(s, 3H); C NMR (CDCl3, 125 MHz): δ202.1, 137.1, 133.1, 126.4, 115.9, 42.1, 32.0,
16.9.
(R,E)/(S,E)-1-{(R)-4-Benzyl-2-thioxothiazolidin-3-yl}-3-hydroxy-6-methylnona-6,8-dien-1-
one(10 & 11). To a solution of thiazolidinethione 9 (4.49 g, 17.8 mmol) in anhydrous CH2Cl2
(55 mL) at -40ᵒC, freshly distilled TiCl4 (2.07 mL, 18.85 mmol) was added drop wise. The
yellowish slurry was stirred for 5 min. at same temp and DIPEA (3.28 mL, 18.85 mmol) was
added drop wise. The deep reddish solution was stirred for another 1h at -40ᵒC before cooling to
-78ᵒC and aldehyde 6 (1.3g, 10.47 mmol in 15 mL CH2Cl2) was cannulated. Stirring was
continued at -78ᵒC for 20 min and quenched by saturated aqueous NH4Cl (15 mL). It was
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extracted with EtOAc, washed with water, brine, dried (Na2SO4), filtered and concentrated in
vacuo. Purification by column chromatography (SiO2, 230-400 mesh, 15%-20% EtOAc in
hexane) separated the two diastereomers 10 and 11 with 69% total yield (dr = 4:1).
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Data for 10; 55% yield, 2.16g, yellowish green liquid; Rf = 0.49 (25% EtOAc in hexane); D
= -44.8 (c 0.3 CHCl3)1H NMR (CDCl3, 500MHz): δ7.37-7.34 (m, 2H), 7.29-7.28(m, 3H),
6.58(dt, J = 16.8, 10.5Hz, 1H), 5.91(d, J = 10.5Hz, 1H), 5.40(m, 1H), 5.12(d, J = 16.8 Hz, 1H),
5.0(d, J=10.5Hz, 1H), 4.13(m, 1H), 3.67(dd, J = 17.7, 2 Hz, 1H), 3.41(dd, J = 11.5, 7.4Hz, 1H),
3.22(dd, J = 13, 3.1Hz, 1H), 3.15(dd, J=17.7, 9.4Hz, 1H), 3.05(dd, J = 13, 10.5Hz, 1H), 2.91(d,
J= 11.5Hz, 1H), 2.75(s, 1H), 2.29-2.23(m, 1H), 2.19-2.14(m, 1H), 1.79(s, 3H), 1.74-1.63(m,
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2H); CNMR( CDCl3, 125MHz): 201.6, 173.3, 138.8, 136.6, 133.4, 129.6, 129.1, 127.5, 126.1,
115.2, 68.5, 67.7, 46.0, 37.1, 35.8, 34.5, 32.3, 16.8 ppm; IR(neat): vmax 3427, 2926, 1695 cm-1;
HRMS (ESI): m/z calculated for C20H25NO2S2Na [M+Na]+ 398.1224, found 398.1225.
Data for 11; 14% yield, 550mg, yellowish green liquid; Rf = 0.57 (25% EtOAc in hexane);
D = -7.3 (c 0.8 CHCl3);1H NMR (CDCl3, 500MHz): δ7.36-7.27(m, 5H), 6.57(dt, J=16.8,
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10.5Hz, 1H), 5.88(d, J=10.5Hz, 1H), 5.41(m, 1H), 5.10(d, J=16.8Hz, 1H), 4.99(d, J=10.5Hz,
1H), 4.04(bs, 1H), 3.48(dd, J= 17.5, 9.3Hz, 1H), 3.40(dd, J= 11.5, 7.3Hz, 1H), 3.34(dd, J=17.5,
2.5Hz, 1H), 3.22(dd, J= 13.0, 3.7Hz, 1H), 3.16(bs, 1H), 3.04(dd, J= 13.0, 10.5Hz, 1H), 2.91(d,
J=11.5Hz, 1H), 2.28-2.23(m,1H), 2.18-2.12(m, 1H), 1.77(s, 3H), 1.75-1.69(m, 1H),1.67-1.60(m,
1H); 13C NMR( CDCl3, 125MHz): δ 201.6, 173.8, 138.8, 136.5, 133. 4, 129.5, 129.1, 127.4,
125.9, 115.1, 68.3, 68.1, 45.6, 36.9, 35.7, 34.7, 32.2, 16.8; IR(neat): vmax 3441, 2924, 1693
cm-1; HRMS (ESI) m/z calculated for C20H25NO2S2Na [M+Na]+ 398.1224, found 398.1223.
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(R,E)-Methyl 3-hydroxy-6-methylnona-6,8-dienoate (12): To a solution of compound 10 (200
mg, 0.53 mmol) in anhydrous methanol (3 mL) at 0ᵒC, imidazole (180.4 mg, 2.65 mmol) was
added and the mixture was stirred overnight at rt. The reaction mixture was then quenched with
saturated solution of NH4Cl (1 mL). Methanol was removed in vacuo and was extracted with
EtOAc, washed with water, brine, dried (Na2SO4) and concentrated in vacuo. Purification by
column chromatography (SiO2, 230-400mesh, 15-20% Et2O in hexane) afforded pure ester 12
(80 mg, 76%) as a colorless oil. Rf = 0.27 (40% Et2O in hexane); D26 = - 5.5 (c 1.2, CHCl3); 1H
NMR (CDCl3, 500MHz): δ6.56(dt, J= 16.8, 10.5Hz, 1H), 5.88(d, J= 10.5Hz, 1H), 5.10(d, J=
16.8Hz, 1H), 4.99(d, J=10.5Hz, 1H), 3.99(bs, 1H), 3.71(s, 3H), 2.91(s, 1H), 2.52(dd, J=16.5,
3.2Hz, 1H), 2.44(dd, J=16.5, 8.9Hz, 1H), 2.26-2.20(m, 1H), 2.16-2.10(m, 1H), 1.76(s, 3H), 1.70-
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1.55(m, 2H); C NMR(CDCl3, 125MHz): δ173.3, 138.6, 133.2, 125.9, 115.0, 67.6, 51.8, 41.1,
35.6, 34.5, 16.6; IR(neat): vmax 3448, 2925, 1735, 1438 cm-1; HRMS (ESI) m/z calculated for
C11H18O3K [M+K]+ 237.0893, found 237.0892.
(S,E)-Methyl 3-hydroxy-6-methylnona-6,8-dienoate(14): Same as ester 12. 78% yield (80 mg)
from compound 11(193 mg), colorless oil; Rf = 0.27 (40% Et2O in hexane); D20 = +12.8(c 0.6
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CHCl3); H NMR (CDCl3, 400MHz): δ6.56(dt, J=16.8, 10.5Hz, 1H), 5.88(d, J=10.5Hz, 1H),
5.10(d, J=16.8Hz,1H), 4.99(d, J= 10Hz, 1H), 3.99(m, 1H), 3.72(s, 3H), 2.90(bs, 1H), 2.52(dd, J=
16.4, 3.3Hz, 1H), 2.43(dd, J=16.4, 8.8Hz, 1H), 2.33-2.20(m, 1H), 2.17-2.10(m, 1H), 1.77(s, 3H),
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1.68-1.60(m, 2H); C NMR(CDCl3, 100MHz): δ173.4, 138.8, 133.4, 126.1, 115.2, 67.8, 51.9,
41.3, 35.8, 34.7, 16.8; IR(neat): vmax 3419, 2925, 1735, 1436 cm-1; HRMS (ESI) m/z calculated
for C11H18O3Na [M+Na]+ 221.1154, found 221.1155.
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(R,E)-Methyl-6-methyl-3-{(S)-3,3,3-trifluoro-2-methoxy-2-phenylpropanoyloxy}nona-6,8-
dienoate (13): To solution of (S)-Mosher’s acid (35 mg, 0.15 mmol) in anhydrous toluene (1
mL) at room temp sequentially DMAP (20.8 mg, 0.17 mmol), Et3N (0.02mL, 0.17mmol) and
2,4,6-trichlorobenzoyl chloride (0.02mL, 0.15 mmol) were added. The white turbid mixture was
stirred for 30 minutes and a solution of alcohol 12 (10mg, 0.05mmol) in dry toluene (0.5 mL)
was then cannulated. After stirring for 4h at room temp, the reaction mixture was quenched with
saturated aqueous NH4Cl (0.5 mL) and extracted with EtOAc. The combined organic extracts
were washed with water, brine, dried (Na2SO4) and concentrated in vacuo. Purification by
column chromatography (silica gel, 100-200mesh, 5% EtOAc in hexane) gave (S)-MTPA ester
13 (16 mg, 76%) as colorless oil. Rf = 0.49 (15% EtOAc in hexane); D26 = -4.7 (c 0.8, CHCl3);
1H NMR (CDCl3, 500MHz) δ7.53(t, J=3.6Hz, 2H), 7.41-7.40(m, 3H), 6.54(dt, J=16.8, 10.5Hz,
1H), 5.82(d, J=10.5Hz, 1H), 5.45(m, 1H), 5.11(d, J=16.8Hz, 1H), 5.02(d, J=10.5Hz, 1Hz),
3.60(s, 3H), 3.53(s, 3H), 2.67(dd, J=16.0, 7.8Hz, 1H), 2.60(dd, J=16.0, 5.1Hz, 1H), 2.09(t,
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J=7.9Hz, 2H), 1.93-1.80(m, 2H),1.74(s, 3H); C NMR(CDCl3, 125MHz): δ170.3, 165.9, 137.4,
133.1, 132.2, 129.7, 128.5, 127.6, 126.5, 115.7, 73.3, 55.5, 51.9, 38.5, 35.2, 32.1,16.6;
IR(neat): vmax 2953, 2926, 1747 cm-1; HRMS (ESI): m/z calculated for C21H25F3O5Na [M+Na]+
437.1552, found 437.1550.
(R,E)-Methyl-6-methyl-3-{(R)-3,3,3-trifluoro-2-methoxy-2-phenylpropanoyloxy}nona-6,8-
dienoate(13a): Same as ester 13. 81% yield (22 mg) from ester 12 (13 mg), colorless oil. Rf =
0.52 (15% EtOAc in hexane) D26 = +19.8 (c 1.0, CHCl3); 1H NMR (CDCl3, 500MHz): δ7.55-
7.53(m, 2H), 7.41-7.39(m, 3H), 6.52(dt, J=16.8, 10.5 Hz, 1H), 5.74(d, J=10.5Hz, 1H), 5.45(m,
1H), 5.09(d, J=16.8Hz, 1H), 5.00(d, J=10.5Hz, 1H), 3.66(s, 3H), 3.55(s, 3H), 2.72(dd, J=16.0,
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7.9Hz, 1H), 2.63(dd, J=16.0, 4.9Hz, 1H), 1.97-1.94(m, 2H), 1.81-1.77(m, 2H), 1.68(s, 3H); C
NMR(CDCl3, 125MHz) δ 170.4, 166.1, 137.5, 133.1, 132.4, 129.7, 128.5, 127.5, 126.4, 115.6,
73.1, 55.6, 52.0, 38.6, 34.8, 31.9, 16.5; IR(neat) vmax 2954, 2925, 1747 cm-1; HRMS (ESI): m/z
calculated for C21H25F3O5Na [M+Na]+ 437.1552, found 437.1553.
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(S,E)-Methyl-6-methyl-3-{(S)-3,3,3-trifluoro-2-methoxy-2-phenylpropanoyloxy}nona-6,8-
dienoate (15): Same as 13. 75% yield (24 mg) from ester 14 (15 mg), colorless oil. Rf = 0.46
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(15% EtOAc in hexane); D = -9.0 (c 1.7, CHCl3); 1H NMR (CDCl3, 500MHz): δ7.54 (t,
J=3.8Hz, 2H), 7.41-7.40(m, 3H), 6.52(dt, J=16.8, 10.5Hz, 1H), 5.74(d, J=10.5Hz, 1H), 5.45(m,
1H), 5.09(d, J=16.8Hz, 1H), 5.00(d, J=10.5Hz, 1H), 3.67(s, 3H), 3.55(s, 3H), 2.73(dd, J=16.0,
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7.9Hz, 1H), 2.63(dd, J=16.0, 4.9Hz, 1H), 1.98-1.94(m, 2H), 1.81-1.77(m, 2H), 1.69(s, 3H); C
NMR (CDCl3, 125MHz) δ 170.5, 166.1, 137.5, 133.2, 132.4, 129.7, 128.5, 127.5, 126.4, 115.6,
73.1, 55.6, 52.1, 38.6, 34.8, 31.9,16.6; IR(neat) vmax 2952, 2927, 1747 cm-1; HRMS (ESI) m/z
calculated for C21H25F3O5Na [M+Na]+ 437.1552, found 437.1552.
(S,E)-Methyl-6-methyl-3-{(R)-3,3,3-trifluoro-2-methoxy-2-phenylpropanoyloxy}nona-6,8-
dienoate (15a): Same as 13. 83% yield (21 mg) from ester 14 (12 mg), colorless oil. Rf = 0.5
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(15% EtOAc in hexane); D = +15.4 (c 0.6, CHCl3); 1H NMR (CDCl3, 500MHz) δ7.54-
7.53(m, 2H), 7.41-7.40(m, 3H), 6.54(dt, J=16.8, 10.5Hz,1H), 5.82(d, J=10.5Hz, 1H), 5.45(m,
1H), 5.11(d, J=16.8Hz, 1H), 5.02(d, J=10.5Hz, 1H), 3.60(s, 3H), 3.53(s, 3H), 2.68(dd, J=16.0,
7.8Hz, 1H), 2.60(dd, J=16.0, 5.1Hz, 1H), 2.09(t, J=7.8Hz, 2H), 1.93-1.80(m, 2H), 1.74(s, 3H);
13C NMR(CDCl3, 125MHz) δ 170.2, 165.9, 137.3, 133.1, 132.2, 129.7,128.5, 127.6, 126.4,
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115.7, 73.2, 55.4, 51.9, 38.4, 35.1, 31.9,16.6; IR(neat):vmax 2952, 2925, 1749 cm-1; HRMS
(ESI): m/z calculated for C21H25F3O5Na [M+Na]+ 437.1552 , found 437.1551.
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(R,E)-3-(tert-Butyldimethylsilyloxy)-6-methylnona-6,8-dienal (5): To ice cold solution of
compound 10 (1.75 g, 4.63mmol) in anhydrous CH2Cl2 (18 mL), 2,6-lutidine (1.26 mL, 11.58
mmol) and TBSOTf (1.38 mL, 6.02 mmol) were added sequentially. The reaction mixture was
stirred from 0ᵒC for 30 min and was quenched by saturated aqueous NaHCO3 (10 mL). The
resulting mixture was extracted with EtOAc. The organic extracts were washed with aqueous
CuSO4, water, brine, dried (Na2SO4), filtered and concentrated in vacuo. Purification by column
chromatography (SiO2, 100-200 mesh, 1.0-1.5% EtOAc in hexane) furnished corresponding TBS
protected compound (2.28g, quantitative) as a greenish-yellow liquid: Rf = 0.5 (5% EtOAc in
hexane); D25 = -87.3 (c 1.5, CHCl3); 1H NMR (CDCl3, 500MHz): δ7.37-7.34(m, 2H), 7.30-
7.28(m, 3H), 6.57(dt, J = 16.8, 10.5Hz, 1H), 5.88(d, J = 10.5Hz, 1H), 5.28(m, 1H), 5.11(d, J =
16.8Hz, 1H), 4.99(d, J = 10.5Hz, 1H), 4.35(m, 1H), 3.58(dd, J = 17.0, 7.8Hz, 1H) 3.35(dd, J =
11, 7.1Hz, 1H), 3.25(dd, J = 13.0, 4.0Hz, 1H), 3.21(dd, J = 17.0, 4.0Hz, 1H), 3.04(dd, J = 13.0,
11.0Hz, 1H), 2.89(d, J = 11.0Hz, 1H,), 2.12(t, J = 7.8Hz, 2H),1.77(s, 3H), 1.67(m, 2H),0.87(s,
9H), 0.1(s, 3H), 0.06(s, 3H); 13C NMR(CDCl3, 125MHz); 201.3, 172.3, 139.2, 136.7, 133.4,
129.6, 129.1, 127.4, 125.7, 114.9, 69.1, 68.8, 45.9, 36.7, 36.0, 35.2, 32.3, 25.9, 18.2, 16.9, -4.3,
-4.5 ppm; IR(neat): vmax 2928, 1697, 1255 cm-1; HRMS (ESI): m/z calculated for
C26H39NO2S2SiNa [M+Na]+ 512.2089, found 512.2088.
The solution of above TBS protected compound (1.2 g, 2.45 mmol) in anhydrous CH2Cl2
(12mL) was cooled to -78ᵒC and DIBAL-H (1.0 M solution in toluene, 4.9mL, 2.0 eq) was added
drop wise till the green solution became colorless. The reaction was then quenched by saturated
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solution of sodium-potassium tartrate (8 mL) and stirred further for 1h till the two layers
separated well. It was then extracted with EtOAc, washed with brine, water, dried (Na2SO4),
filtered and concentrated in vacuo. Quick flash column chromatography (SiO2, 230-400 mesh,
3% EtOAc in hexane) yielded aldehyde 5 (616mg, 89%) as yellow liquid. Rf = 0.56 (5% EtOAc
in hexane); 1H NMR (CDCl3, 500MHz): δ 9.81(d, J = 2 Hz, 1H), 6.56(dt, J = 16.8, 10.5 Hz, 1H),
5.84(d, J = 10.5 Hz, 1H), 5.10 (d, J = 16.8 Hz), 4.99 (d, J = 10.5Hz), 4.19 (m, 1H), 2.54(dd, J =
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6.0,2.0 Hz, 2H), 2.12-2.05(m, 2H), 1.76(s, 3H), 1.69-1.64(m, 2H); C NMR(CDCl3, 125MHz):
δ 202.2, 138.7, 133.3, 125.9, 115.2, 68.0, 50.9, 36.1, 35.4, 25.9, 18.1, 16.8, -4.28, -4.48 ppm.
(3S,5R,E)-1-{(S)-4-Benzyl-2-thioxothiazolidin-3-yl}-5-(tert-butyldimethylsilyloxy)-3-
hydroxy-8-methylundeca-8,10-dien-1-one (17): To a solution of thiazolidinethione 16 (935
mg, 3.71 mmol) in CH2Cl2 (12 mL) at -40ᵒC, freshly distilled TiCl4 (0.43mL, 3.92 mmol) was
added drop wise. The yellow slurry was stirred for 5 min. DIPEA (0.68mL, 3.92mmol) was
added drop wise and stirred for another 2h at -40ᵒC. Reaction mixture was cooled to -78ᵒC and
aldehyde 5 (616mg, 2.18 mmol, in 10 mL of CH2Cl2) was then cannulated. The reaction was
continued further at -78ᵒC for 20 min and quenched by cold saturated aqueous NH4Cl (10 mL),
extracted with EtOAc, washed with water, brine, dried (Na2SO4), filtered and concentrated in
vacuo. Purification by column chromatography (SiO2, 230-400mesh, 8-10 % EtOAc in hexane)
afforded 17 (698 mg, 60%) as yellow oil. Rf = 0.33 (15% EtOAc in hexane); D25 = +53.1(c
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2.0, CHCl3); H NMR (CDCl3, 500MHz): δ7.36-7.26(m, 5H), 6.57(dt, J= 16.8, 10.5Hz, 1H),
5.87(d, J=10.5Hz, 1H), 5.39(m,1H), 5.11(d, J=16.8Hz, 1H), 5.00(d, J=10.5Hz, 1H), 4.52(m,
1H), 4.04-4.00(m, 1H), 3.45(dd, J=17.5, 2.9Hz,1H), 3.39(dd, J= 11.5, 7.2Hz, 1H), 3.29(dd,
J=17.5, 9.0Hz, 1H), 3.25(dd, J=13.0, 3.6Hz, 1H), 3.05(dd, J=13.0, 10.7 Hz, 1H), 2.89(d,
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J=11.5Hz, 1H), 2.09-2.06(m, 2H), 1.78(s, 3H), 1.76-1.71(m, 3H), 1.64(ddd, J=14.0, 6.0, 2.2Hz,
1H), 0.91(s, 9H), 0.12(s, 3H), 0.1(s, 3H); 13C NMR(CDCl3, 125MHz): δ201.4, 172.5, 139.1,
136.6, 133.4, 129.6, 129.0, 127.4, 125.7, 115.0, 70.6, 68.6, 64.9, 46.8, 41.6, 36.9, 35.7, 34.9,
32.2, 25.9, 18.1, 16.9, -4.4, -4.5; IR(neat): vmax 3502, 2951, 2928, 1697, 1684 cm-1; HRMS
(ESI): m/z calculated for C28H43NO3S2SiNa [M+Na]+ 556.2351, found 556.2350.
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ethoxy]diphenylsilane (20): Data for compound 2014. Rf = 0.42 (5% EtOAc in hexane); D
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=+23.3 (c 0.3, CHCl3); HNMR (CDCl3, 500MHz): δ7.67-7.65(m, 4H), 7.43-7.36(m, 6H),
6.57(dt, J = 16.8, 10.5Hz, 1H),5.86(d, J = 10.5Hz, 1H), 5.08(d, J = 16.8Hz, 1H), 4.98(d, J =
10.5Hz, 1H), 4.08(m, 1H), 3.81-3.65(m, 3H), 2.18-2.13(m, 1H), 2.10-2.04(m, 1H), 1.76(s, 3H),
1.74-1.62(m, 3H), 1.58(m, 3H), 1.34(s, 3H), 1.32(s, 3H), 1.04(s, 9H); 13C
NMR(CDCl3,125MHz): δ139.0, 135.7, 134.1, 134.0, 133.5, 129.7, 127.8, 125.9, 114.8, 100.4,
66.2, 63.6, 60.2, 39.1, 38.9, 35.7, 34.0, 27.0, 24.9, 19.4, 16.7; IR(neat): vmax 2933, 1110 cm-1;
HRMS (ESI): m/z calculated for C31H44O3SiNa [M+Na]+ 515.2957, found 515.2956.
(3S,5R,E)-Methyl-5-(tert-butyldimethylsilyloxy)-3-hydroxy-8-methylundeca-8,10-dienoate
(19):Same as 12. 78% (95 mg) from compound 17(183 mg), colourless oil. Rf = 0.43 (15%
EtOAc in hexane); D25 = +7.7(c 0.8 , CHCl3); 1H NMR (CDCl3, 500MHz): δ 6.56(dt, J = 16.8,
10.5z, 1H), 5.80(d, J = 10.5Hz), 5.10(dd, J = 16.8, 1.5Hz, 1H), 4.98(dd, J = 10.5, 1.5Hz, 1H),
4.35-4.31(m, 1H), 4.02-3.98(m, 1H), 3.71(s, 3H), 3.60(d, J = 2.3Hz, 1H), 2.51(dd, J = 16.0,
8.0Hz, 1H), 2.44(dd, J = 16.0, 4.7Hz, 1H), 2.07-2.04(m, 2H), 1.76(s, 3H), 1.73-1.57(m, 4H),
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0.90(s, 9H), 0.1(s, 3H), 0.09(s, 3H); C NMR(CDCl3, 125MHz): δ 172.9, 139.1, 133.4, 125.7,
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115.1, 70.6, 65.2, 51.8, 42.2, 41.7, 35.7, 35.1, 26.0, 18.2, 16.9, 0.2, -4.4, -4.5; IR(neat): vmax
3444, 2925, 2854, 1734 cm-1; HRMS (ESI): m/z calculated for C19H36O4SiNa [M+Na]+
379.2281, found 379.2282.
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(3S,5R,E)-Methyl-3,5-dihydroxy-8-methylundeca-8,10-dienoate {Ieodomycin A(1)}
&
(4S,6R,E)-4-hydroxy-6-(3-methylhexa-3,5-dienyl)-tetrahydropyran-2-one {Ieodomycin B
(2)}: A solution of ester 19 (51 mg, 0.14 mmol) in CH2Cl2 & MeOH (1:1, 2mL) was cooled to
0ᵒC and CSA (3.3mg, 0.014mmol) was added at once. The reaction mixture was then stirred at
room temp for 30 min. before quenching with Et3N. The solution was concentrated and purified
by column chromatography (Neutral alumina, 25%- 45% EtOAc in hexane) to yield Ieodomycin
A (1) and Ieodomycin B(2).
Ieodomycin A(1): Eluted with 25% EtOAc in hexane, 35% yield {12 mg together with
Ieodomycin B(2)}; Rf = 0.32 (50% EtOAc in hexane) 1H NMR (CD3OD, 500MHz): δ 6.57(dt, J
= 16.8, 10.6Hz, 1H), 5.87(d, J = 10.6Hz, 1H), 5.04(d, J = 16.8Hz, 1H), 4.94(d, J = 10.6Hz, 1H),
4.26(m, 1H), 3.77(m, 1H), 3.67(s, 3H), 2.50(dd, J = 15.5, 4.8Hz, 1H), 2.44(dd, J = 15.0, 8.2Hz,
1H), 2.19(m, 2H), 2.11(m, 1H), 1.76(s, 3H), 1.59-1.52(m, 4H); IR(neat): vmax 3409, 2929, 1734,
1438 cm-1; HRMS (ESI): m/z calculated for C13H22O4Na [M+Na]+ 265.1416, found 265.1417.
Ieodomycin B(2): Eluted with 45% EtOAc in hexane, colorless oil, 54% yield (19 mg); Rf = 0.16
(50% EtOAc in hexane); D23 = +25.8 (c 0.5, CHCl3); 1H NMR (CD3OD, 500MHz): δ 6.59(dt,
J = 16.7, 10.5 Hz, 1H), 5.89(d, J = 10.5Hz, 1H), 5.07(d, J = 16.7 Hz, 1H), 4.97(d, J = 10.5Hz,
1H), 4.26(m, 1H), 4.19(m, 1H), 2.86(dd, J = 17.0, 5.6, 1H), 2.36(dd, J = 17.0, 7.1Hz, 1H),
2.28(m, 1H), 2.26(m,1H), 2.18(m, 1H), 1.80(m, 2H), 1.78(s, 3H), 1.52(ddd, J = 13.3,11.5,8.7Hz,
1H); 13C NMR(CDCl3,125MHz): δ 174.1, 139.1, 134.6, 127.7, 115.7, 78.6, 64.5, 40.3, 38.8, 36.2,
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35.0, 16.7; IR(neat): vmax 2922, 1716 cm-1 ; HRMS (ESI): m/z calculated for C12H18O3Na
[M+Na]+ 233.1154, found 233.1155.
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(3R,5R,E)-1-{(S)-4-Benzyl-2-thioxothiazolidin-3-yl}-5-(tert-butyldimethylsilyloxy)-3-
hydroxy-8-methylundeca-8,10-dien-1-one(18): yellow oil, 12% (140 mg) from aldehyde 5(616
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mg), Rf = 0.61 (20% EtOAc in hexane); D = -52.8(c 1.4, CHCl3); H NMR (CDCl3, 500
MHz): δ7.36-7.33(m, 2H), 7.30-7.28(m, 3H), 6.57(dt, J = 16.9, 10.5 Hz, 1H), 5.86(d, J = 10.5
Hz, 1H), 5.40(m, 1H), 5.10(d, J = 16.9 Hz, 1H), 4.99(d J = 10.5 Hz, 1H), 4.33(m, 1H), 3.97(m,
1H), 3.56(dd, J = 18, 3.5 Hz, 1H), 3.39(dd, J = 11.5, 7.2 Hz, 1H), 3.30-3.20(m, 2H), 3.04(dd, J =
13.0, 10.6 Hz, 1H), 2.89(d, J = 11.5 Hz, 1H), 2.09(m, 2H), 1.77(s, 3H), 1.74-1.61(m, 4H), 0.90(s,
9H), 0.11(s, 3H), 0.10(s, 3H) ; 13C NMR (CDCl3, 125 MHz) δ 201.5, 172.7, 139.3, 136.6, 133.4,
129.6, 129.1, 127.4, 125.7, 115.0, 71.3, 68.5, 66.6, 46.4, 42.9, 36.9, 35.7, 35.1, 32.2, 26.0, 18.2,
16.9, -4.0, -4.3 ppm; IR(neat): vmax 3535, 2927,1693,1255 cm-1; HRMS (ESI): m/z calculated
for C28H43NO3S2SiNa [M+Na]+ 556.2351, found 556.2352.
(3R,5R,E)-Methyl-5-(tert-butyldimethylsilyloxy)-3-hydroxy-8-methylundeca-8,10-dienoate
(21): Same as compound 19. 73% yield (63 mg) from 18 (130 mg), colorless oil. Rf = 0.51(20%
EtOAc in hexane); D27 = +4.1(c 1.3, CHCl3); 1H NMR (CDCl3, 500 MHz): δ 6.56(dt, J = 16.6,
10.6Hz, 1H), 5.84(d, J = 10.6Hz, 1H), 5.10(d, J = 16.6Hz, 1H), 4.99(d, J =10.6Hz, 1H), 4.17(bs,
1H), 3.94(m, 1H), 3.71(s,3H), 3.40(s,1H), 2.49(d, J = 5.8Hz, 2H), 2.07(t, J = 8.1Hz, 2H), 1.76(s,
3H), 1.73-1.62(m, 4H), 0.90(s, 9H), 0.1(s, 3H), 0.09(s, 3H); 13C NMR (CDCl3, 125 MHz) δ
172.9, 139.2, 133.4, 125.7, 115.0, 71.5, 66.9, 51.8, 42.8, 41.8, 35.7, 35.1, 26.0, 18.1, 16.9, -4.0, -
4.4 ppm; IR(neat): vmax 3473, 2952, 2929, 1735 cm-1; HRMS (ESI): m/z calculated for
C19H36O4SiNa [M+Na]+ 379.2281, found 379.2282.
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(4R,6R,E)-4-Hydroxy-6-(3-methylhexa-3,5-dienyl)-tetrahydropyran-2-one (2a): To a stirred
solution of compound 21 (52 mg, 0.15 mmol) in dry THF (1.5 mL), TBAF (1M solution in THF,
0.22 mL, 0.22 mmol) was added at 0ᵒC. Reaction mixture was stirred for 1 h at same
temperature. It was quenched with saturated aqueous NH4Cl (1 mL), extracted with EtOAc,
washed with water, brine, dried (Na2SO4), filtered and concentrated in vacuo. Purification by
column chromatography (SiO2, 230-400 mesh, 8-10% EtOAc in hexane eluant) afforded pure
compound 2a (22 mg, 70%) as a colorless oil. Rf = 0.41(60% EtOAc in hexane); D23 = +11.9(c
0.3, CHCl3);1H NMR (CD3OD, 500 MHz): δ 6.59(dt, J = 16.8, 10.5Hz, 1H), 5.90(d, J = 10.5Hz,
1H), 5.07(dd, J = 16.8, 1.5Hz, 1H), 4.99(dd, J = 10.5, 1.2Hz, 1H), 4.28-4.24(m, 1H), 4.22-
4.17(m, 1H), 2.86(dd, 17, 5.3Hz, 1H), 2.37(dd, J = 17, 7.1Hz, 1H), 2.29-2.24(m, 2H), 2.21-
2.15(m, 1H), 1.80(m, 2H), 1.78(s, 3H), 1.52(ddd, J = 13.0, 12.0, 8.6Hz, 1H); 13C NMR (CD3OD,
125 MHz): δ 173.8, 139.2, 134.6, 127.7, 115.7, 77.5, 63.5, 39.3, 36.6, 36.1, 35.2, 16.7 ppm;
IR(neat): vmax 3427, 2920, 1708,1257 cm-1; HRMS (ESI): m/z calculated for C12H18O3Na
[M+Na]+ 233.1154, found. 233.1153.
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(3S,5S,E)-1-{(S)-4-Benzyl-2-thioxothiazolidin-3-yl}-5-(tert-butyldimethylsilyloxy)-3-
hydroxy-8-methylundeca-8,10-dien-1-one (22): yellow oil; 45.7%(292 mg) overall yield from
11(450 mg); Rf = 0.59 (20% EtOAc in hexane); D25 = +57.8(c 1.5, CHCl3); 1H NMR (CDCl3,
500 MHz): δ7.36-7.33(m, 2H), 7.30-7.28(m, 2H), 6.57(dt, J = 16.8, 10.5, 1H), 5.86(d, J =
10.5Hz, 1H), 5.40(m, 1H), 5.10(d, J = 16.8 Hz, 1H), 4.99(d, J = 10.5 Hz, 1H), 4.33(m, 1H),
3.97(m, 1H), 3.56(dd, J = 17.5, 3.1Hz, 1H), 3.39(dd, J = 13, 10.5 Hz, 1H), 3.27-3.21(m, 2H),
3.04(dd, J = 13, 10.5Hz, 1H), 2.89(d, J = 11.5 Hz, 1H), 2.09(m, 2H), 1.77(s, 3H), 1.75-1.64(m,
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4H), 0.9(s, 9H), 0.11(s, 3H), 0.1(s, 3H); C NMR (CDCl3, 125 MHz) δ 201.5, 172.7, 139.3,
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136.6, 133.4, 129.6, 129.1, 127.4, 125.7, 114.9, 71.3, 68.5, 66.6, 46.4, 42.9, 36.9, 35.7, 35.2,
32.2, 26.1, 18.2, 16.9, -4.0, -4.3 ppm; IR(neat): vmax 3417, 2927, 1699 cm-1; HRMS (ESI): m/z
calculated for C28H43NO3S2SiNa [M+Na]+ 556.2351, found 556.2350.
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(3S,5S,E)-Methyl-5-(tert-butyldimethylsilyloxy)-3-hydroxy-8-methylundeca-8,10-dienoate
(24): Same as compound 19. 76% yield (106 mg) from compound 22 (210 mg), colorless liquid.
Rf = 0.12 (10% EtOAc in hexane); D25 = -12.1(c 1.3, CHCl3); 1H NMR (CDCl3, 500 MHz): δ
6.56( dt, J = 16.7, 10.5Hz, 1H), 5.84(d, J = 10.5 Hz. 1H), 5.10(d, J = 16.7Hz, 1H), 4.99(d, J =
10.5 Hz, 1H), 4.17(m, 1H), 3.94(m, 1H), 3.71(s, 3H), 3.40(s, 1H), 2.49(d, J = 5.9Hz, 2H), 2.07(t,
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J = 8.1Hz, 2H), 1.76(s, 3H), 1.71-1.58(m, 4H), 0.90(s, 9H), 0.1(s, 6H); C NMR (CDCl3, 75
MHz) δ 172.9, 139.2, 133.4, 125.7, 115.0, 71.5, 66.9, 51.8, 42.8, 41.8, 35.7, 35.1, 26.0, 18.1,
16.9, -4.0, -4.4 ppm; IR(neat): vmax 3519, 2953, 2929, 1738 cm-1; HRMS (ESI): m/z calculated
for C19H36O4SiNa [M+Na]+ 379.2281, found 379.2281.
(4S,6S,E)-4-Hydroxy-6-(3-methylhexa-3,5-dienyl)-tetrahydropyran-2-one (2b): Same as
compound 2a. 71% yield (40 mg) from compound 24 (95 mg), colorless liquid; Rf = 0.42 (60%
1
EtOAc in hexane); D23 = -9.35(c 0.3, CHCl3); H NMR (CD3OD, 500 MHz): δ 6.59(dt, J =
16.8, 10.5Hz, 1H), 5.89(d, J = 10.5Hz, 1H), 5.08(d, J = 16.8Hz, 1H), 4.98(d, J = 10.5Hz, 1H),
4.26(m, 1H), 4.20(m, 1H), 2.87( dd, J = 17, 5.7 Hz, 1H), 2.37(dd, J = 17.0, 7.0Hz, 1H), 2.31-
2.25(m, 2H), 2.21-2.15(m, 1H), 1.80(m, 2H), 1.78(s, 3H), 1.56-1.49(m, 1H); 13C NMR (CD3OD,
125 MHz): δ 173.5, 139.2, 134.63, 127.7, 115.7, 77.5, 63.5, 39.3, 36.6, 36.1, 35.2, 16.7; IR
(neat): vmax 3425,2923, 1708, 1255 cm-1; HRMS (ESI): m/z calculated for C12H18O3Na
[M+Na]+ 233.1154, found 233.1155.
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(3R,5S,E)-1-{(S)-4-Benzyl-2-thioxothiazolidin-3-yl}-5-(tert-butyldimethylsilyloxy)-3-
hydroxy-8-methylundeca-8,10-dien-1-one (23): yellow oil; 14% overall yield(90 mg) from
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500 MHz): δ 7.36-7.33(m, 2H), 7.30-7.28(m, 3H), 6.57(dt, J = 16.9, 10.5 Hz, 1H), 5.86(d, J =
10.5 Hz, 1H), 5.39(m, 1H), 5.11(d, J = 16.9 Hz, 1H), 5.00(d, J = 10.5Hz, 1H), 4.52(m, 1H),
4.04-3.99(m, 1H), 3.59(bs, 1H), 3.45(dd, J = 17.5, 2.9 Hz, 1H), 3.40(dd, J = 11.5, 7.2 Hz), 3.32-
3.23(m, 2H), 3.05(dd, J = 13, 10.6 Hz, 1H), 2.89(d, J = 11.5 Hz, 1H), 2.09-2.06(m, 2H), 1.78(s,
3H), 1.76-1.72(m, 2H), 1.67-1.61(m, 2H), 0.91(s, 9H), 0.12(s, 3H), 0.1(s, 3H); 13C NMR
(CDCl3, 125 MHz) δ201.5, 172.6, 139.1, 136.7, 133.4, 129.7, 129.1, 127.4, 125.7, 115.0, 70.7,
68.7, 64.9, 46.8, 41.7, 36.9, 35.7, 35.1, 32.2, 26.0, 18.1, 16.9, -4.4, -4.5 ppm; IR(neat): vmax
3485, 2927, 1699, 1257 cm-1; HRMS (ESI): m/z calculated for C28H43NO3S2SiNa [M+Na]+
556.2351, found 556.2352.
(3R,5S,E)-Methyl-5-(tert-butyldimethylsilyloxy)-3-hydroxy-8-methylundeca-8,10-dienoate
(25): Same as compound 19. 77% (42 mg) overall yield from 23 (82 mg); colorless liquid; Rf =
24
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0.45 (15% EtOAc in hexane); D = -13.2 (c 0.8, CHCl3); H NMR (CDCl3, 500 MHz) δ
6.56(dt, J = 16.8, 10.5 Hz, 1H), 5.84(d, J = 10.5Hz, 1H), 5.10(d, J = 16.8Hz, 1H ), 4.99(d, J =
10.5 Hz, 1H), 4.33(bs, 1H), 3.99(m, 1H), 3.71(s, 3H), 3.61(s, 1H), 2.51(dd, J = 16, 8 Hz, 1H),
2.44(dd, J = 16, 4.5 Hz, 1H), 2.06-2.03(m, 2H), 1.76(s, 3H), 1.72-1.63(m, 4H), 0.89(s, 9H),
0.1(s, 3H), 0.8(s, 3H); 13C NMR (CDCl3, 125 MHz) δ172.9, 139.1, 133.4, 125.7, 115.1, 70.6,
65.2,51.8, 42.2, 41.7, 35.7, 35.0, 26.0, 18.1, 16.9, -4.4, -4.5 ppm; IR(neat): vmax 3435, 2926,
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1741, 1585 cm-1; HRMS (ESI): m/z calculated for C19H36O4SiNa [M+Na]+ 379.2281, found
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379.2282.
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(4R,6S,E)-4-Hydroxy-6-(3-methylhexa-3,5-dienyl)-tetrahydropyran-2-one (2c): same as
compound 2a. 83% yield (17 mg) from compound 25 (35 mg), colorless oil; Rf = 0.42 (60%
1
EtOAc in hexane); D23 = -18.2 (c 0.3, CHCl3); H NMR (CD3OD, 500 MHz): δ 6.58(dt, J =
16.8, 10.6Hz, 1H), 5.88(d, J = 10.6Hz, 1H), 5.07(d, J = 16.8 Hz,1H), 4.97(d, J = 10.6Hz, 1H),
4.28-4.22(m, 1H), 4.19(m, 1H), 2.86(dd, J = 17, 5.5Hz, 1H), 2.36(dd, J = 17.0, 7.0Hz, 1H), 2.28-
2.24(m, 2H), 2.20-2.17(m, 1H), 1.80(m, 2H), 1.77(s, 3H), 1.51(ddd, J = 13.8, 12.0, 8.6 Hz, 1H);
13C NMR (CD3OD, 125 MHz): δ 174.2, 139.1, 134.6, 127.7, 115.7, 78.5, 64.4, 40.2, 38.7, 36.2,
35.1, 16.7 ppm; IR (neat): vmax 3417, 1925, 1728, 1249cm-1; HRMS (ESI): m/z calculated for
C12H18O3Na [M+Na]+ 233.1154, found 233.1153.
ASSOCIATED CONTENT:
13
Supporting Information: General experimental procedure, Table-2, copies of NMR (1H, C),
HRMS of representative compounds; 2D NMR (COSY, NOESY, ROSEY) of compound 2.
These material are available free of charge via the Internet at http://pub.acs.org.
AUTHOR INFORMATION:
Corresponding Author
*E-mail: ocrkg@iacs.res.in
ACKNOWLEDGEMENTS:
SD thanks to CSIR, New Delhi, India for research fellowship. The author acknowledges jointly
IACS and DST (project no. SR/FT/CS-157/2011) for financial support to carry over this work.
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14. Preparation of compound 20 and characteristic 13C value:
1. NaBH4, MeOH, 0oC, 15min, 83%
24.9
24.9
2. CSA, CH2Cl2:MeOH(1:1), 0oC-rt,
100.4
2h, 92%
O
O
17
OTBDPS
3. TBDPS-Cl, Et3N, DMAP
CH2Cl2, 0oC-rt 2h, 88%
4. 2,2-DMP, CSA, CH2Cl2
0oC-rt, 2h, 79%
20
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16. Personal communications between us and the Koul group indicates that the peak below 1.6
ppm is also present in the NMR spectrum of Ieodomycin B and was overlooked in the original
report by Shin.
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